The invention relates to a method for cold-start pre-warming of a pressure-charged internal combustion engine and/or of an exhaust gas aftertreatment device of a pressure-charged internal combustion engine. The invention furthermore relates to a motor vehicle, in particular a commercial vehicle, having a pressure-charged internal combustion engine, an exhaust gas aftertreatment device and a device for cold-start pre-warming of the pressure-charged internal combustion engine and/or of an exhaust gas aftertreatment device.
The fact that pollutant emissions from an internal combustion engine can be reduced in an effective manner by catalytic aftertreatment of the exhaust gas with the aid of an exhaust gas aftertreatment system, e.g., one having an exhaust gas catalyst, is known from practical experience. However, it is an important precondition for this that the catalyst has reached its light off temperature. Below this temperature, the exhaust gas catalyst is ineffective or not very effective, and the reaction takes place only at insufficiently low conversion rates.
In systems with exhaust gas turbocharging, reaching catalyst light off in an optimum manner for emissions is critical, owing to the heatsink provided by the exhaust turbine. In the case of internal combustion engines of this kind, it is thus necessary to take precautions to ensure that the exhaust gas catalyst reaches its light off temperature quickly when cold starting.
Use is frequently made of secondary air systems to limit cold starting emissions. In this case, secondary air is injected close to the outlet valves during warmup, e.g., by means of a secondary air pump. By means of the reaction of the injected air with the unburnt exhaust gas constituents contained in the hot exhaust gases and further oxidation in the catalyst, the catalyst is heated up more quickly.
For this purpose, DE 44 41 164 A1 proposes, for example, to deliver the charge air to the internal combustion engine via a charge air line and to arrange a throttle valve inside this charge air line. A recirculated air line leading to the inlet side of the charger branches off upstream of the throttle valve and downstream of the charger. A recirculated air adjuster is arranged in the recirculated air line. A connecting line leads from the pressure side of the charger to an exhaust line of the internal combustion engine, wherein a control valve connected to an engine control unit is arranged in the connecting line.
The disadvantage with the previously known approaches is that additional components, e.g., a secondary air pump, a recirculated air line, a recirculated air adjuster, and a throttle valve have to be provided.
Cold-starting aids for preheating the combustion air in the form of a flame-starting device or of a glow plug, which are arranged in the intake air duct of the combustion device, are furthermore known in practice. In particular, a cold-starting aid of this kind serves to allow cold starting of internal combustion engines, e.g., diesel engines or spark-ignition engines, with or without charge air. It is used, particularly in the case of diesel engines, such as direct injection diesel engines for use on trucks, to ensure reliable starting of the engine at low temperatures of, for example, below −10° C. The disadvantage with these cold-starting aids is that the warming effect is restricted to the charge air temperature and that there is no heating of the cylinders or of the exhaust gas aftertreatment device.